For the paddles, Left side down, right side up, seems cumbersome to me.

The "push downshift, pull upshift" on either side in my 35i seem correct and convenient.

If I am in the middle of a hard 90 degree turn and my right hand is crossed over my body to the left and I need to shift, EITHER UP OR DOWN, I can do so with my right hand.

In the same situation with the "left side down, right side up" set up, you would only be able to shift up with your right hand. To shift down, you'd have to cross your left arm over or under your right arm to get to the left side paddle which is now on the right since the wheel has been turned. That seems awkward.
Plus, one can use the "pull up, push down" system as a "left side down, right side up" system if desired. All you have to do is not use the other function on each paddle.

So, this begs the question... What benefit was gained by switching to a "left side down, right side up" set up?

Having had the 2011 with both paddles the same I always preferred the paddles on my Ferrari...right for up shifts and left for down shifts, so having both cars the same is now easier for me. Your points are also valid, and on the Ferrari the paddles are NOT connected to the steering wheel so they are always in the same position. Photo attached.